The goal set for the current year is to proceed as planning by infusing the remainder of our projected subject population. There have been no major changes in the direction of the study as planned. The objective of the project remains to investigate the pharmacology and physiology of panic disorders. Our basic goals include: to understand the mechanism of induction of panic attack by lactate; to specify the physiological chain of events associated with panic, with emphasis on the sequence of antecedent shifts; to examine the changes which occur with the infusion of lactate, and contrast patients and normal controls in this regard; to determine to what extent the physiological objective measures covary with each other and with the subjective sensations; and, to understand the mode of action of imipramine as a therapeutic agent blocking panic attacks. Our adjunct goals include the following; to ascertain the diagnostic specificity of lactate-induced panic attacks by infusing other psychiatric populations; to evaluate the effectiveness of other drugs in blocking panic; to isolate the property of lactate which precipitates a panic; and finally, to determine whether or not patients acquire tolerance to repeated infusions.